Ginger Stuyvesant is an American heiress living in London during World War I. She's engaged to Captain Benjamin Hartshorne, a young intelligence officer. This is a world where the spiritualist movement really works, and Ginger is a medium for The Spirit Corps, which is a like a secretarial pool composed of mediums. Before deployment, each soldier going to the front is conditioned to report in to the mediums of the Spirit Corps before passing on to the Beyond, so the Corps can pass instant information about troop movements on to military intelligence.The work is exhausting but valuable, and Ginger and her fellow mediums contribute a great deal to the war efforts, until things start to get personal. One day a soldier insults her while she is walking with Ben, and the next day he reports in dead: but not due to war wounds; he has been murdered by another man living at the base. Military Intelligence also begins to receive reports that the Spirit Corps is now being directly targeted by the German war effort.And then the day comes that Ginger has dreaded for her entire career, and Ben is the next soldier to report in.

But he was not killed in the war as she feared, but murdered by a mysterious assailant who clearly knew how to avoid being spotted by the Spirit Corps. But unlike other ghosts who disappear as soon as their report is given. He clearly has unfinished business: to find his murderer and finish his investigation into how the Germans are targeting the Spirit Corps. But now that he is dead, he will have to rely on Ginger to serve as his bodily agent, a difficult and dangerous task for a woman of that age. But this time, at least, both the spirit and the flesh are willing.